A universal law for the pattern evolution of fullerene-based sandwiches

TL;DR

This paper presents a universal law describing the pattern evolution in fullerene-based sandwiches, revealing how their structures transform based on area ratios, with implications for designing nanomaterials for electronics and energy storage.

Contribution

It introduces an analytical model predicting pattern transformations and critical area ratios in fullerene sandwiches, validated by molecular dynamics simulations and experimental data.

Findings

Pattern transforms from circular to rectangular at area ratio 1/π.

Critical vacuum space predicted at 34 Å, matching experiments.

Structural transformation driven by energy competition, informing material design.

Abstract

Fullerene-based sandwiches have emerged as new candidates for potential applications of two-dimensional nanomaterials in electronics or energy storage. Recently, experimentalists have observed the evolution of boundaries for fullerene clusters sandwiched by two graphene layers, while vacuum space with typical dimension of 30 {\AA} was found within the fullerene layer. Because the pattern of the fullerene cluster impacts the physical properties of the sandwiches, it is important to understand the mechanisms for their structural transformations. In the present work, we find that the graphene/fullerene/graphene sandwich structure transforms among three configurations, depending on the fullerene to graphene area ratio. Molecular dynamics simulations show that there are two critical values for the area ratio. The fullerene pattern transforms from circular to rectangular at the first critical area ratio of 1/{\pi}. The critical value of 1/{\pi} is successfully derived by comparing the geometrical perimeter of the circular and rectangular shapes for the fullerene cluster without any physical parameters. At the second critical area ratio, the graphene layers surrounding the fullerene cluster become separated due to the competition between the bending energy and the cohesive energy. Based on the analytic model, the vacuum space is predicted to be 34 {\AA}, which agrees quite well with the experimental result. These findings provide fundamental insights into the mechanisms driving structural transformation of fullerene-based sandwiches, which will enable the selection of appropriate structures and materials to guide the design of future electronic and energy storage applications.